viz_browser_tests is seen to flake in ~5% of CQ runs on win7_chromium_rel_ng. The actual tests that fail seem to be random. Here are some examples:

https://ci.chromium.org/buildbot/tryserver.chromium.win/win7_chromium_rel_ng/138166
PredictorBrowserTest.DontPredictBasedOnSubresources

https://ci.chromium.org/buildbot/tryserver.chromium.win/win7_chromium_rel_ng/138126
PolicyToolUITest.DefaultSession

https://ci.chromium.org/buildbot/tryserver.chromium.win/win7_chromium_rel_ng/138083
SupervisedUserBlockModeTest.Unblock/0

https://ci.chromium.org/buildbot/tryserver.chromium.win/win7_chromium_rel_ng/138023
PolicyToolUITest.DefaultSession

https://ci.chromium.org/buildbot/tryserver.chromium.win/win7_chromium_rel_ng/137822
StartupBrowserCreatorTest.ProfilesWithoutPagesNotLaunched


These all seem to be actual test failures. For example:

[ RUN      ] SupervisedUserBlockModeTest.Unblock/0
[4816:3420:0404/225709.799:WARNING:discovery_network_list_win.cc(195)] Failed to open Wlan client handle: 1062
[4816:2184:0404/225709.830:INFO:profile_sync_service.cc(2174)] ConfigureDataTypeManager not invoked because engine is not initialized
[4816:2184:0404/225709.846:WARNING:chrome_browser_main_win.cc(630)] Command line too long for RegisterApplicationRestart:  --brave-new-test-launcher --cfi-diag=0 --gtest_also_run_disabled_tests --gtest_filter=SupervisedUserBlockModeTest.Unblock/0 --single_process --test-launcher-bot-mode --test-launcher-filter-file=../../testing/buildbot/filters/viz.browser_tests.filter --test-launcher-output="C:\Users\CHROME~2\AppData\Local\Temp\scoped_dir304_13690\results304_13467\test_results.xml" --test-launcher-summary-output="e:\b\swarm_slave\w\io98f1rk\output.json" --user-data-dir="C:\Users\CHROME~2\AppData\Local\Temp\scoped_dir304_13690\d304_20962" --disable-offline-auto-reload --host-resolver-rules="MAP *.example.com 127.0.0.1:62927,MAP *.new-example.com 127.0.0.1:62927,MAP *.a.com 127.0.0.1:62927" --managed-user-id=asdf --no-first-run --no-default-browser-check --enable-logging=stderr --disable-default-apps --wm-window-animations-disabled --disable-component-update --test-type=browser --force-color-profile=srgb --disable-zero-browsers-open-for-tests --ipc-connection-timeout=30 --allow-file-access-from-files --dom-automation --log-gpu-control-list-decisions --disable-backgrounding-occluded-windows --disable-gl-drawing-for-tests --override-use-software-gl-for-tests --force-color-profile=srgb --disable-compositor-ukm-for-tests --enable-features=TestFeatureForBrowserTest1,VizDisplayCompositor --disable-features=NetworkPrediction,TestFeatureForBrowserTest2 --flag-switches-begin --flag-switches-end --restore-last-session about:blank
[2592:2388:0404/225709.877:INFO:media_foundation_video_encode_accelerator_win.cc(370)] Windows versions earlier than 8 are not supported.
[4816:2184:0404/225710.274:FATAL:interstitial_page_impl.cc(644)] Check failed: false.
Backtrace:
	base::debug::StackTrace::StackTrace [0x03722230+32]
	base::debug::StackTrace::StackTrace [0x036E734D+13]
	logging::LogMessage::~LogMessage [0x0368DE93+83]
	content::InterstitialPageImpl::Proceed [0x02556282+98]
	SupervisedUserService::OnSiteListUpdated [0x056A246F+79]
	SupervisedUserURLFilter::SetContents [0x056A56B0+176]
	base::internal::FunctorTraits<void (__thiscall content::VideoDecoderShim::*)(std::unique_ptr<content::VideoDecoderShim::PendingFrame,std::default_delete<content::VideoDecoderShim::PendingFrame> >),void>::Invoke<base::WeakPtr<content::VideoDecoderShim>,std [0x0572965B+47]
	base::internal::Invoker<base::internal::BindState<void (__thiscall policy::URLBlacklistManager::*)(std::unique_ptr<policy::URLBlacklist,std::default_delete<policy::URLBlacklist> >),base::WeakPtr<policy::URLBlacklistManager> >,void __cdecl(std::unique_ptr< [0x038BFDCD+61]
	base::OnceCallback<void __cdecl(std::unique_ptr<SupervisedUserURLFilter::Contents,std::default_delete<SupervisedUserURLFilter::Contents> >)>::Run [0x056A711C+48]
	base::internal::ReplyAdapter<std::unique_ptr<SupervisedUserURLFilter::Contents,std::default_delete<SupervisedUserURLFilter::Contents> >,std::unique_ptr<SupervisedUserURLFilter::Contents,std::default_delete<SupervisedUserURLFilter::Contents> > > [0x056A6F8C+44]
	base::internal::FunctorTraits<void (__cdecl*)(base::OnceCallback<bool __cdecl(void)>,bool *),void>::Invoke<base::OnceCallback<bool __cdecl(void)>,bool *> [0x0281D1DB+43]
	base::internal::Invoker<base::internal::BindState<void (__cdecl*)(base::OnceCallback<void __cdecl(bool,history::URLRow const &,std::vector<history::VisitRow,std::allocator<history::VisitRow> > const &)>,history::QueryURLResult const *),base::OnceCallback< [0x0281D199+41]
	base::internal::PostTaskAndReplyImpl::PostTaskAndReply [0x037338A4+1348]
	base::debug::TaskAnnotator::RunTask [0x0371E8FD+237]
	base::internal::IncomingTaskQueue::RunTask [0x03741D49+105]
	base::MessageLoop::RunTask [0x036C2E27+519]
...


I'm not sure whether these failures are specific to viz_browser_tests or whether browser_tests are failing more generally, but this is affecting the CQ and causing a significant number of jobs to be retried. Marking P1. Please diagnose this. Thanks.